One or more time division duplex (TDD) configurations may be implemented by a plurality of serving cells (cells or carriers equivalently) in a wireless network for communications to wireless devices or user equipment (UE). Implementing a given TDD configuration at a base station may include using a downlink-to-uplink switch-point periodicity associated with a number of subframes for downlink and uplink respectively. In order to increase the peak data rate, carrier aggregation may be implemented in which UEs are served by multiple cells simultaneously. When carrier aggregation is applied in a TDD system, different TDD configurations can be applied for serving cells in each radio frequency band to have more flexibility in TDD operation.